Cutting tool for breaking mineral and artificial materials

ABSTRACT

The invention relates to the mining industry, in particular to a cutting tool for breaking mineral and artificial materials. The inventive tool comprises a working head provided with a hard-alloy insert on one end thereof and a three-part stem on the other end. A clamping sleeve made of elastic material is arranged on the second part of the stem and provided with a slopping element in order to prevent said sleeve from the displacement thereof longitudinally with respect to the stem A protective element provided with a through hole, in which the first part of the stem can be accommodated, is disposed at a distance ranging from 0.6 to 0.85 of the length of the clamping sleeve with respect to the end of said sleeve oriented towards the working head along the longitudinal symmetrical axis of the tool, the diameter of the first part of the stem is larger than the diameter of the third part thereof. Said invention makes it possible to improve the operating reliability of the tool by reducing the deformation of the clamping sleeve by the protective element by shaping said clamping sleeve in such a way that it is conical.

FIELD OF THE INVENTION

The instant invention relates to the mining industry, in particular to a cutting tool for breaking mineral and artificial materials, and may be used in the effectors of mining and boring machines during the mining of mineral deposits and the formation of excavations in the earth, and also in actuators of road-building machines during the building and repair of roads.

BACKGROUND ART

A cutting tool for breaking mineral and artificial materials is known that is adapted for being mounted with the possibility for free rotation in a channel of a support secured on an actuator, the tool having the form of a body of revolution with a longitudinal axis of symmetry. The tool comprises a working head, an insert made of a hard-alloy material and secured to one end of the working head, and a stem connected to the other end of the working head. The stem comprises a first part arranged on one end of the stem from the side of the working head, a second part adjacent the first part and having a diameter less than the diameter of the first part, and a third part adjacent the second part, positioned on the other end of the stem and having a diameter that is not less than the diameter of the second part. A split clamping sleeve of cylindrical form is arranged on the second part of the stem and has a stopping element serving to fix it from movements along the longitudinal axis of symmetry of the tool relative to the stem. A protective element has a through axial hole and is mounted on the clamping sleeve (see, for example, laid-open German application No. 19630642, class E21 C 35/18, published 5 Feb. 1998).

In the known tool, in order to arrange the stem in the axial channel of the support, the clamping sleeve is deformed by applying an impact load to the tool in the axial direction. A drawback of this technical solution is the large labor expenditure of the work in respect to mounting the tool in the channel of the support, which is due to the necessity of providing deformation of the clamping sleeve in constrained conditions, in particular during the replacement directly on the actuator of a tool that has become inoperative. Furthermore, the aforesaid dynamic action on the clamping sleeve during the mounting of the tool may result in a change of its geometrical shape, which may result in disturbance of the conditions for free rotation of the stem in the channel of the support during operation.

A cutting tool for breaking mineral and artificial materials is also known that is adapted for being mounted with the possibility for free rotation in a channel of a support secured on an actuator, the tool having the form of a body of revolution with a longitudinal axis of symmetry. The tool comprises a working head, an insert made of a hard-alloy material and secured to one end of the working head, and a stem connected to the other end of the working head. The stem comprises a first part arranged on one end of the stem from the side of the working head, a second part adjacent the first part and having a diameter less than the diameter of the first part, and a third part adjacent the second part, positioned on the other end of the stem and having a diameter that is not less than the diameter of the second part. A split clamping sleeve of cylindrical form is made of an elastic material, is arranged on the second part of the stem and has a stopping element serving to fix it from movement along the longitudinal axis of symmetry of the tool relative to the stem. A protective element has a through axial hole with a diameter exceeding the diameter of the first part of the stem, and is mounted on the clamping sleeve with the possibility for axial movement along the sleeve for positioning it on the first part of the stem during the installation of the cutting tool in the support (see, for example, laid-open German application No. 19720635, class E21C 35/18, published 19 Nov. 1998).

This tool partially removes the drawbacks of the earlier described tool, since it eliminates the necessity for dynamic action on the clamping sleeve during the mounting of the tool. In this tool the clamping sleeve is deformed to a size ensuring its free passage into the axial channel of the support by putting a protective element on the sleeve. In such a condition the tool is inserted into the channel of the support and then the protective element is moved onto the first part of the stem, thus freeing the clamping sleeve. The clamping sleeve under the action of the elastic force expands in the channel of the support and fixes the fool in the latter.

A drawback of this technical solution is the necessity for relatively strong deformation of the clamping sleeve in order to obtain a diameter less than the diameter of the channel in the support. After such compression, residual deformations appear in the clamping sleeve, which after removal of the protective element may result in that the clamping sleeve will not reliably hold the stem in the channel of the support to a sufficient degree. Preliminary compression during the mounting of the tool and subsequent expansion of the clamping sleeve may result in a disturbance of its geometrical shape and, consequently, disturbance of the free rotation of the stem in the channel of the support in the process of operation.

The object of the instant invention is to create a cutting tool for breaking mineral and artificial materials, the construction of which would ensure reliable fixation of the tool in the channel of a support while simultaneously providing convenience in mounting under operation conditions.

SUMMARY OF THE INVENTION

This object is achieved in that a cutting tool for breaking mineral and artificial materials, adapted for installation with the possibility for free rotation in a channel of a support secured on an actuator, the tool having the form of a body of revolution with a longitudinal axis of symmetry and comprising a working head, an insert made of a hard-alloy material and secured to one end of the working head, a stem connected to the other end of the working head and comprising a first part arranged on one end of the stem from the side of the working head, a second part adjacent the first part and having a diameter less than the diameter of the first part, and a third part adjacent the second part, positioned on the other end of the stem and having a diameter that is not less than the diameter of the second part, a split clamping sleeve made of an elastic material, arranged on at least the second part of the stem and having a stopping element serving to fix it against movement along the longitudinal axis of symmetry of the tool relative to the stem, a protective element having a through axial hole with a diameter exceeding the diameter of the first part of the stem and mounted on the clamping sleeve with the possibility for axial movement along the sleeve for positioning it on the first part of the stem during the installation of the cutting tool in the channel of the support. In accordance with the invention the protective element is disposed at a distance ranging from 0.6 to 0.85 of the length of the clamping sleeve with respect to the end of the sleeve oriented towards the working head along the longitudinal axis of symmetry of the tool, wherein the diameter of the first part of the stem is greater than the diameter of the third part thereof.

The aforesaid construction of the tool provides for a conical shape of the clamping sleeve inserted into the support, which ensures a reduction of the laboriousness of mounting under operating conditions with a simultaneous reduction of the degree of deformation of the clamping sleeve by the protective element, as a result of which the reliability of both parts of the tool and fixation of the stem in the support is enhanced.

The diameter of the through hole in the protective element may exceed the diameter of the channel of the support.

In that case the diameter of the clamping sleeve prior to insertion of the tool into the channel of the support is greater than the diameter of the channel of the support. Such a structural solution is related to the fact that during lengthy storage of the tools, a clamping sleeve made of an elastic material (for example, spring steel) and being in a compressed state “tires” and after removal of the protective element may not assume the necessary geometrical parameters. In that case the reliability of fixation of the cutting tool in the channel of the support is impermissibly reduced. The proposed construction increases the reliability of fixation of the tool in the support.

The protective element may be made in the form of a flat washer. With such a variant of structural embodiment of the protective element, the abrasive wear of tool units during operation is reduced, which improves the conditions for free rotation of the stem in the channel of the support.

The protective element may be made in the form of a washer having a U-shaped form in cross section. With such a variant of structural embodiment of the protective element, additional protection of the support and parts of the tool against eroded material is provided.

The protective element may be made in the form of a disk spring washer. With such a variant of structural embodiment of the protective element, a reduction of the dynamic loads on parts of the tool is ensured and this results in enhancement of the operation reliability of the tool.

The washer may be provided with an annular projection positioned along the through axial hole of the washer, facing the third part of the stem and adapted for arrangement in a corresponding input aperture of the channel of the support, which makes it possible to ensure better centering of the stem relative to the clamping sleeve and the channel of the support, and, consequently, improve the conditions for rotation of the stem in that channel.

The clamping sleeve may be arranged on the second and third parts of the stem, and its length along the longitudinal axis of symmetry of the tool may exceed the sum length of the second and third parts of the stem along that axis, which ensures an additional reduction of the laboriousness of mounting the tool in the channel of the support while simultaneously reducing wear of the channel of the support.

The stopping element may be made in the form of at least one projection positioned on the inner surface of the clamping sleeve, while the second part of the stem may have an annular recess for the arrangement of that projection. With such a variant of the structural embodiment, the reliability of the connection of the stem to the clamping sleeve increases.

The stopping element may be made in the form of three projections, uniformly positioned along the circumference of the cross section of the inner surface of the clamping sleeve, the center of which is positioned on the longitudinal axis of symmetry of the tool, which ensures enhancement of the conditions of free rotation of the stem in the channel of the support as a result of centering of the stem relative to the clamping sleeve.

The projection on the clamping sleeve may be made in the form of a figured tongue, which makes it possible to reduce the laboriousness of making the tool.

The length of the clamping sleeve along the longitudinal axis of symmetry of the tool may be less than the length of the second part of the stem along that axis, which ensures an additional reduction of laboriousness of mounting the tool in the support.

The stopping element may be an end surface of the clamping sleeve, which surface faces the third part of the stem, this making it possible to simplify the construction of the tool.

The two surfaces of the clamping sleeve that are formed when it is split may be positioned parallel to the longitudinal axis of symmetry of the tool. Such a variant of embodiment makes it possible to improve the exit of broken material from the annular channel formed by the inner surface of the clamping sleeve and the outer surface of the stem, which improves the conditions for free rotation of the stem in the channel of the support.

The two surfaces of the clamping sleeve that are formed when it is split may be positioned inclined to the plane passing through the longitudinal axis of symmetry of the tool. This also makes it possible to additionally improve the exit of broken material from the annular channel formed by the inner surface of the clamping sleeve and the outer surface of the stem, and consequently improve the conditions for free rotation of the stem in the channel of the support.

The tool my have equal angles of inclination of the two surfaces, formed when the sleeve is split, relative to the plane passing through the longitudinal axis of symmetry of the tool. This makes it possible to somewhat reduce the laboriousness of making the tool.

Each surface, formed during the split of the clamping sleeve, may be made helical. This makes it possible to improve the exit of broken material from the annular channel formed by the inner surface of the clamping sleeve and the outer surface of the stem, which improves the conditions for free rotation of the stem in the channel of the support.

The insert may comprise a base secured on the working head, an intermediate part adjacent the base and formed by a body of revolution with an outer side surface of concave shape, and a head part adjacent the intermediate part and formed by a body of revolution with an outer side surface of convex shape, smoothly matching the outer side surface of the intermediate part. With such a variant of structural embodiment of the insert, the conditions for free rotation of the stem in the channel of the support are additionally enhanced and simultaneously stability of the level of the load on the parts of the tool are maintained for the whole period of operation of the latter, which makes it possible to increase the operational reliability of the tool.

The length of the intermediate part of the insert along the longitudinal axis of symmetry of the tool may not exceed the length of the head part of the insert along that axis.

The length of the head part of the insert along the longitudinal axis of symmetry of the tool may not exceed the length of the intermediate part of the insert along that axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first variant of embodiment of a cutting tool for breaking mineral and artificial materials, in accordance with the invention.

FIG. 2—a second variant of embodiment of the tool, in accordance with the invention.

FIG. 3—a third variant of embodiment of the tool, in accordance with the invention.

FIG. 4—a fourth variant of embodiment of the tool, in accordance with the invention.

FIG. 5—a fifth variant of embodiment of the tool, in accordance with the invention.

FIG. 6—a clamping sleeve of the tool.

FIG. 7—a perspective view of another variant of embodiment of the clamping sleeve.

FIG. 8—a view along the arrow A in FIG. 6.

FIG. 9—a protective element of the tool.

FIG. 10—an insert of the working head of the tool.

FIG. 11—front view with a section cut of the tool mounted in the support.

FIG. 12—front view with a section cut of the tool mounted in the support in another variant of embodiment.

DETAILED DESCRIPTION OF THE PREFERABLE VARIANTS OF EMBODIMENT OF THE INVENTION

The cutting tool for breaking mineral and artificial materials has the form of a body of revolution with a longitudinal axis of symmetry and comprises a working head 1 (FIGS. 1-5), which may have any geometrical shape, preferably the form of a body of revolution. An insert 3 made of a hard-alloy material is secured on one end 2 of the working head 1. Preferably, the insert 3 has the shape of a body of revolution and may be secured on the working head 1 with the aid of any known undetachable or detachable connection, preferably, with the aid of soldering.

A stem 4 has the form of a body of revolution and may be made as an integer whole with the working head 1 or connected to another end 5 of the head 1 with the aid of a detachable or undetachable connection. The stem 4 comprises a first part 6, positioned at one end of the stem 4 from the side of the working head 1, a second part 7, adjacent part 6, and a third part 8, adjacent part 7 and positioned on the other end of the stem 4. The diameter of part 6 is greater than the diameter of part 7 or part 8.

A cut clamping sleeve 9 of cylindrical form, made from an elastic material, for example, steel, is arranged on at least part 7 (FIG. 3).

The sleeve 9 has a stopping element 10 serving to fix it from movement along the longitudinal axis of symmetry of the tool relative to the stem 4.

A protective element 11 with a through axial hole 12 (FIG. 9) is mounted on the clamping sleeve 9 with the possibility for axial movement. The protective element 11 serves to reduce the wear of the facing each other surfaces of respectively the stem 4 and support 13 of the cutting tool (FIGS. 11, 12), and also to prevent the ingress of the broken material (slack) into annular channel 14 formed by the inner surface of the clamping sleeve 9 and the side surface of the stem 4. The diameter D of the through axial hole 12 in the protective element 11 exceeds the diameter d of the first part 6 of the stem 4, that is the condition: D>d, is fulfilled. The protective element 11 is positioned at a distance K, which is not less than 0.6 and not more than 0.85 the length M of the clamping sleeve 9 along longitudinal axis 15 of symmetry of the tool relative to end 16 of the clamping sleeve 9, which faces the working head 1, that is the condition: 0.6 M<K<0.85 M, is fulfilled. Wherein, base point 17, to which the value of the distance K is determined, is taken to be the point of the beginning of contact of the protective element 11 with the clamping sleeve 9 from the side of the working head 1. The values of the range of geometrical ratios between the parts of the tool, which are indicated above, have been obtained in an empirical manner. In the case where the geometrical ratios extend beyond the upper limit of the indicated range, an arbitrary sliding of the protective element 11 from the clamping sleeve 9 may occur during transportation of the tool or when it is being mounted in the support 13. In the case where the geometrical ratios extend beyond the lower limit of the indicated range, the clamping sleeve 9 will not acquire a conical shape which is the optimum shape for mounting the tool in the support 13. The diameter d of the first part 6 of the stem 4 exceeds the diameter C of its third part 8, i.e., the condition: C<d, is fulfilled. Fulfillment of this condition makes it possible to give the clamping sleeve 9 the shape of a truncated cone during the mounting of the tool in the support 13. In the case where the condition indicated above between the diameters of the first part 6 and the third part 8 of the stem 4 is not fulfilled, its part 8 will prevent the formation of a conical shape of the clamping sleeve 9 during the mounting of the tool in the support 13.

The protective element 11 may have any geometrical shape, mainly the form of a body of revolution, and additionally provides deformation of the clamping sleeve 9, thus ensuring that the latter takes on the predetermined geometrical shape during the mounting of the tool in the support 13. The most advisable variant is that variant of the structural embodiment of the protective element 11 wherein it is made in the form of a flat washer (FIG. 2), i.e., the face surfaces of the washer are planes. In the case of such a variant of structural embodiment of the protective element 11 it is preferable that it be made with an annular projection 18 (FIGS. 3, 11) positioned along the through axial hole 12 of the protective element 11, facing the third part 8 of the stem 4 and adapted for arrangement in a corresponding input hole 19 of channel 20 of the support 13 (FIGS. 11, 12). The projection 18 and corresponding hole 19 may have any geometrical shape.

The protective element 11 may be made in the form of a washer having a U-shaped form in cross section (FIG. 12). In that case it is most advisable that this washer be made with an annular axial projection 18 positioned along the hole of the washer and facing the third part 8 of the stem 4 for arrangement in a corresponding input hole 19 of channel 20 of the support 13.

The protective element 11 may be made in the form of a disk spring washer (FIG. 9). In that case it is most advisable that this washer also be made with the annular projection 18 described above for arrangement in input hole 19 of channel 20 of the support 13.

It is preferable that the diameter of the through hole 12 of the protective element 11 exceed the diameter of the channel 20 of the support 13, as is shown in FIGS. 11, 12. Such a construction increases the reliability of securing the tool in the support.

In accordance with one of the variants of structural embodiment of the device, the clamping sleeve 9 is arranged on the second part 7 and third part 8 of the stem 4 and its length M along the longitudinal axis 15 of symmetry of the tool exceeds the sum of the length L of the second part 7 of the stem 4 and the length S of the third part 8 of the stem 4 along the same axis 15, that is the condition: M>L+S, is fulfilled. This ratio of the geometrical parameters of the parts of the tool determines that the end of the clamping sleeve 9 extends beyond the end face of the stem 4 (FIGS. 1, 2, 11). With such a variant of structural embodiment of the clamping sleeve 9 its stopping element 10 may be made in the form of at least one projection positioned on the inner surface of the clamping sleeve 9, and the stem 4 has a recess 21 for the accommodation of that projection (FIGS. 1, 2, 4, 11). The projection forming the stopping element 10 on the clamping sleeve 9 may be made in the form of a separate part, secured on the clamping sleeve 9 with the aid of a detachable or undetachable connection, or be made by pressing a section of the clamping sleeve 9 inwards, i.e., may be made as one whole with the clamping sleeve 9. Most advisable is execution of the stopping element 10 in the form of three projections (FIGS. 6, 8), which are positioned uniformly along the circumference of the cross section of the inner surface of the clamping sleeve 9, the center of which lies on the longitudinal axis 15 of symmetry of the tool. The projection on the clamping sleeve 9 that forms the stopping element 10 may be made in the form of a figured tongue (FIG. 6). The figured tongue may be obtained by making a U-shaped through slot on the side surface of the clamping sleeve 9. Then the section of the clamping sleeve, which is limited by the aforesaid U-shaped through slot, is bent back into the inner cavity of the clamping sleeve 9.

In accordance with another variant of structural embodiment of the device, the length M of the clamping sleeve 9 along the longitudinal axis 15 of symmetry of the tool may be less than the length L of the second part 7 of the stem 4 (FIGS. 3, 12), i.e., the condition: M<L , is fulfilled. The indicated ratio of the geometrical parameters of the parts of the tool determine that the clamping sleeve 9 may be positioned within the limits of the second part 7 of the stem 4. With such a variant of structural embodiment of the clamping sleeve 9, the end face surface 22 may be its stopping element 10 (FIGS. 7, 12).

The split clamping sleeve 9 has surfaces 23, 24, formed when it is split. During a split of the sleeve 9 an additional channel 25 is formed for the passage of the broken material (slack). The configuration of the additional channel 25 for passage of the broken products may be of any form. It is preferable that the surfaces 23, 24, formed during the split of the clamping sleeve 9, be positioned parallel to the longitudinal axis 15 of symmetry of the tool. Thus, in FIGS. 1,3, a clamping sleeve 9 is shown, the surfaces 23, 24 of which are positioned parallel to the longitudinal axis 15 of symmetry of the device. One of the variants of structural embodiment of the clamping sleeve 9 provides for the surfaces 23, 24, formed during the split of the clamping sleeve 9, being positioned inclined to the plane passing through the longitudinal axis 15 of symmetry of the tool (FIGS. 2, 6). Wherein, the angles of inclination of the surfaces 23, 24 relative to the aforesaid plane may be equal. In accordance with another variant of structural embodiment of the clamping sleeve, each surface 23, 24, formed during the split of the clamping sleeve 9, may have the shape of a helical surface.

The insert 3 of hard-alloy material may comprise a head part 26, a base 27 secured to the working head 1, and an intermediate part 28 positioned between the head part 26 and base 27 (FIG. 10). The intermediate part 28 of the insert 2 is formed by a body of revolution with an outer side surface of concave shape. Wherein, the head part 26 of the insert is formed by a body of revolution with an outer side surface of convex shape. The side surface of the head part 26 of the insert 3 smoothly conjugates with the side surface of its intermediate part 28. In accordance with one of the variants of structural embodiment of the tool, the length E of the intermediate part 28 of the insert 3 along the longitudinal axis 15 of symmetry of the tool should not exceed the length F of the head part 26 of the insert 3 along that same axis 15, i.e., the condition: E<F , is fulfilled. In accordance with another variant, the length F of the head part 26 of the insert 3 along the longitudinal axis 15 of symmetry of the tool should not exceed the length E of the intermediate part 28 of the insert 3 along that same axis 15, i.e., the condition: F<E , should be fulfilled.

The cutting tool for breaking mineral and artificial materials operates in the following manner.

At first the tool is mounted in the channel 20 of the support 13, which is secured on an actuator (not shown in the drawings). In order to do this, the clamping sleeve 9 is mounted on the stem 4. Then the clamping sleeve 9 is pressed to a diameter less than the diameter D of the protective element 11. The protective element 11 is put on the clamping sleeve 9, arranging it at a certain distance K from the end 16 of the clamping sleeve 9 that faces the working head 1. After the protective element occupies the indicated position, the clamping sleeve 9 is freed, and it expands under the action of elastic force. The protective element 11 prevents further expansion of the clamping sleeve 9, and it, as a result of application of off-center force created by the protective element 11, takes on the form of a truncated cone, the peak of which is oriented towards the third part 8 of the stem 4. Wherein, the protective element 11 holds the clamping sleeve 9 in a compressed state, ensuring a predetermined form of the clamping sleeve 9 during the mounting of the tool. Further, the tool is inserted into the channel 20 of the support 13 until there is interaction between the protective element 11 and the end of the support 13. Wherein, it should be noted that giving the clamping sleeve 9 the shape of a truncated cone ensures its free entrance into the channel 20 of the support 13. Then an axial force is applied to the working head 1, under the action of which the protective element 11, abutting against the end of the support 13, moves in an axial direction along the clamping sleeve 9 in the direction toward the working head 1, while the stem 4 together with the clamping sleeve 9 enters the channel 20 of the support 13. The aforesaid introduction of the stem 4 into the channel 20 will continue until the protective element 11 completely moves to the first part 6 of the stem 4. When the protective element 11 moves to part 6 of the stem 4, it frees the clamping sleeve 9, which under the action of elastic force expands and is pressed against the walls of the channel 20 of the support 13. Thus, the clamping sleeve 9 is fixed relative to the support 13. Movement of the stem 4 along the longitudinal axis 15 of symmetry of the tool relative to the clamping sleeve 9 according to one of the variants of structural embodiment of the tool (FIGS. 1, 2, 11) is hindered by the stopping element 10, made in the form of at least one projection, which after the tool is mounted turns out to be placed in the recess 21 of the stem 4. According to another variant of the structural embodiment of the tool (FIGS. 3, 12), the indicated movement of the stem 4 relative to the clamping sleeve 9 is prevented by the stopping element 10, i.e., the end surface 22 of the clamping sleeve 9, which after the tool is mounted interacts with the third part 8 of the stem 4.

During movement of the actuator on which the support 13 is secured with the aid of a detachable or undetachable connection, the working head 1 with the insert 3 of hard-alloy material enters into interaction with the broken material. As a result of action of external forces appearing in the process of interaction of the working head 1 and the insert 3 with the material being broken, the stem 4 freely turns about the longitudinal axis 15 of symmetry of the tool in the channel 20 of the support 13, thus ensuring uniform wear of the parts of the tool interacting with the material being broken. The protective element 11 protects the support 13 from interaction with the material being broken, promotes free rotation of the tool in the channel 20 of the support 13 and reduces the wear of the working head 1 and the support 13. After wear of the insert 3 or the working head 1 or after they have broken, the defective tool is replaced by a new tool, the mounting of which is carried out in the manner described above. It should be noted that during lengthy storage of the tool in a warehouse, residual deformation of the clamping sleeve 9 may appear, i.e., the clamping sleeve 9, taking the shape of a truncated cone under the effect of the protective element 11, partially maintains that shape and after the tool is positioned in the channel 20 of the support 13. Even in that case, the reliability of securing the tool in the support is maintained, since the most loaded end of the clamping sleeve 9, facing the working head 1, remains virtually undeformed during storage. 

1. A cutting tool for breaking mineral and artificial materials, adapted for installation with the possibility for free rotation in a channel of a support secured on an actuator, the tool having the form of a body of revolution with a longitudinal axis of symmetry and comprising a working head, an insert made of a hard-alloy material and secured to one end of the working head, a stem connected to the other end of the working head and comprising a first part arranged on one end of the stem from the side of the working head, a second part adjacent the first part and having a diameter less than the diameter of the first part, and a third part adjacent the second part, positioned on the other end of the stem and having a diameter that is not less than the diameter of the second part, a split clamping sleeve made of an elastic material, arranged on at least the second part of the stem and having a stopping element serving to fix it against movement along the longitudinal axis of symmetry of the tool relative to the stem, a protective element having a through axial hole with a diameter exceeding the diameter of the first part of the stem and mounted on the clamping sleeve with the possibility for axial movement along the sleeve for positioning it on the first part of the stem during the installation of the cutting tool in the channel of the support, characterized in that the protective element is disposed at a distance ranging from 0.6 to 0.85 of the length of the clamping sleeve with respect to the end of the sleeve oriented towards the working head along the longitudinal axis of symmetry of the tool, wherein the diameter of the first part of the stem is greater than the diameter of the third part thereof.
 2. The tool according to claim 1, characterized in that the diameter of the through hole in the protective element exceeds the diameter of the channel of the support.
 3. The tool according to claim 1, characterized in that the protective element is made in the form of a flat washer.
 4. The tool according to claim 1, characterized in that the protective element is made in the form of a washer having a U-shaped form in cross section.
 5. The tool according to claim 1, characterized in that the protective element is made in the form of a disk spring washer.
 6. The tool according to claim 3, characterized in that the washer is provided with an annular projection positioned along a through axial hole of the washer, facing the third part of the stem and adapted for arrangement in a corresponding input aperture of the channel of the support of the tool.
 7. The tool according to claim 1, characterized in that the clamping sleeve is arranged on the second and third parts of the stem, and its length along the longitudinal axis of symmetry of the tool exceeds the sum length of the second and third parts of the stem along that axis.
 8. The tool according to claim 7, characterized in that the stopping element is made in the form of at least one projection positioned on an inner surface of the clamping sleeve, while the second part of the stem has an annular recess for the arrangement of that projection.
 9. The tool according to claim 8, characterized in that the stopping element is made in the form of three projections uniformly positioned along the circumference of the cross section of the inner surface of the clamping sleeve, the center of which is positioned on the longitudinal axis of symmetry of the tool.
 10. The tool according to claim 8, characterized in that the projection on the clamping sleeve is made in the form of a figured tongue.
 11. The tool according to claim 1, characterized in that the length of the clamping sleeve along the longitudinal axis of symmetry of the tool is less than the length of the second part of the stem along that axis.
 12. The tool according to claim 11, characterized in that the stopping element is an end surface of the clamping sleeve, which surface faces the third part of the stem.
 13. The tool according to claim 1, characterized in that the two surfaces of the clamping sleeve that are formed when it is split are positioned parallel to the longitudinal axis of symmetry of the tool.
 14. The tool according to claim 1, characterized in that the two surfaces of the clamping sleeve that are formed when it is split are positioned inclined to a plane passing through the longitudinal axis of symmetry of the tool.
 15. The tool according to claim 14, characterized in that it has equal angles of inclination of the two surfaces that are formed when the sleeve is split, relative to the plane passing through the longitudinal axis of symmetry of the tool.
 16. The tool according to claim 1, characterized in that the insert comprises a base secured on the working head, an intermediate part adjacent the base and formed by a body of revolution with an outer side surface of concave shape, and a head part adjacent the intermediate part and formed by a body of revolution with an outer side surface of convex shape, smoothly matching the outer side surface of the intermediate part.
 17. The tool according to claim 16, characterized in that the length of the intermediate part of the insert along the longitudinal axis of symmetry of the tool does not exceed the length of the head part of the insert along that axis.
 18. The tool according to claim 16, characterized in that the length of the head part of the insert along the longitudinal axis of the tool does not exceed the length of the intermediate part of the insert along that axis. 